The present invention relates generally to a method for preparing ketones using reactants such as ketones and carboxylic acids. In one embodiment, it relates to an entirely new process for the production of unsymmetrical ketones from ketones and carboxylic acids over a ceria-alumina catalyst system in the temperature range of 300.degree. to 550.degree. C. utilizing a very short contact time over the catalyst to achieve a conversion in the range of 85 percent or more while recovering most of the unconverted reactants for recycling. An excellent example of such a reaction is the reaction of acetone with pivalic acid over a ceria-alumina catalyst to produce pinacolone.
Pinacolone is an intermediate which is useful in the preparation of pharmaceutical products and pesticides for which improved methods of manufacture have been sought for some time now. An electrolytic reductive coupling of acetone to form pinacol which can be converted to pinacolone has been carried out on an experimental basis for a number of years to produce small quantities of pinacol, but such processes have thus far failed to receive much commercial utilization because of the cost factors involved in these methods.
A thermo-chemical route as taught by literature utilizes a pyrolysis of one or two carboxylic acids to yield symmetrical or unsymmetrical ketones, respectively. This type of reaction has been used commercially with the significant disadvantage that the raw materials used in the manufacture of the ketones are costly because the selectivity of the reaction to unsymmetrical ketones is low.
The article Thermal Behavior of Aliphatic and Alicyclic Ketones, J. Chem. Soc. Japan, Vol. 87, No. 10 (1966) pp. 1108-1110 by Furukawa and Naruchi describes observations of work done in the study of the thermal decomposition of ketones. In the course of this work, ketones were reacted together at 500.degree. C. in the presence of calcium carbonate. The authors do not show the production of ketones from a ketone and a carboxylic acid or carboxylic acid precursor nor do they show any recycle features. This article may tend to indicate the possibility of "equilibrating" two symmetric ketones to form an unsymmetrical ketone and the possibility of "equilibrating" an unsymmetric ketone to two different symmetric ketone, but the discussion on p. 10 (English translation) indicates that this is not the case.
Therefore, as with all chemical processes, it would be very desirable to be able to reduce the cost of a thermo-chemical route to the pinacolone or other ketones for use in the chemical industry on a commercial basis.